Stents, grafts and a variety of other endoprostheses are well known and used in interventional procedures, such as for treating aneurysms, lining or repairing vessel walls, filtering or controlling fluid flow, and expanding or scaffolding occluded or collapsed vessels. Such endoprostheses can be delivered and used in virtually any accessible body lumen of a human or animal and can be deployed by any of a variety of recognized means.
An endoprosthesis is typically delivered by a catheter system to a desired location or deployment site inside a body lumen of a vessel or other tubular organ. To facilitate such delivery, the endoprosthesis must be capable of having a particularly small crossing profile to reach the desired deployment site, which may be difficult to access by the treating physician through the tortuous pathway of the patient's anatomy. Therefore, it would be desirable to provide the endoprosthesis with a sufficient degree of longitudinal flexibility during delivery to allow advancement through the anatomy to the deployed site.
Once deployed, the endoprosthesis should be capable of satisfying a variety of performance characteristics. The endoprosthesis should have sufficient rigidity or outer bias to perform its intended function, such as opening a lumen or supporting a vessel wall. Similarly, the endoprosthesis should have suitable flexibility along its length when deployed so that it will not kink or straighten when deployed in a curved vessel. In certain application, the endoprosthesis should provide an elevated and consistent degree of scaffolding of the vessel wall and prevent plaque from protruding into the artery, for example during the treatment of atherosclerosis in the carotid arteries. Therefore, it would be desirable for the endoprosthesis to provide a substantially uniform or otherwise controlled scaffolding of the vessel wall.
One type of endoprosthesis is the stent, which is used for the treatment of atherosclerotic stenosis in blood vessels. After a patient undergoes a percutaneous transluminal angioplasty or similar interventional procedure, a stent may be deployed at the treatment site to maintain patency of the vessel. The stent is configured to scaffold or support the treated blood vessel and may be loaded with a beneficial agent, acting as a delivery platform to reduce restenosis or the like.
Numerous endoprosthesis designs and constructions have been developed to address one or more of the performance characteristics summarized above. For example, a variety of stent designs are disclosed in the following patents: U.S. Pat. No. 4,580,568 to Gianturco; U.S. Pat. No. 5,102,417 to Palmaz; U.S. Pat. No. 5,104,404 to Wolff; U.S. Pat. No. 5,133,732 to Wiktor; U.S. Pat. No. 5,292,331 to Boneau; U.S. Pat. No. 5,514,154 to Lau et al.; U.S. Pat. No. 5,569,295 to Lam; U.S. Pat. No. 5,707,386 to Schnepp-Pesch et al.; U.S. Pat. No. 5,733,303 to Israel et al.; U.S. Pat. No. 5,755,771 to Penn et al.; U.S. Pat. No. 5,776,161 to Globerman; U.S. Pat. No. 5,895,406 to Gray et al.; U.S. Pat. No. 6,033,434 to Borghi; U.S. Pat. No. 6,099,561 to Alt; U.S. Pat. No. 6,106,548 to Roubin et al.; U.S. Pat. No. 6,113,627 to Jang; U.S. Pat. No. 6,132,460 to Thompson; U.S. Pat. No. 6,331,189 to Wolinsky et al.; and U.S. Pat. No. 7,128,756 to Lowe et al., the entireties of which are incorporated herein by reference.
Certain endoprosthesis structures in the prior art are based on joining a plurality of web rings disposed longitudinally with connectors that increase the flexibility of the endoprosthesis by providing preferred bending points. One example of a stent in the prior art is illustrated in FIG. 1, in which a plurality of web rings 10 (shown in a flattened configuration), are joined one to the other by connectors 12. The individual web rings 10 are formed by a plurality of web elements 14 that are sequentially adjoined at junction bends 16.
While the endoprosthesis of FIG. 1 is shown as having web elements 14 of rectilinear design, endoprosthesis having web elements of different designs are also known in the art. For example, U.S. Patent Application Publication Nos. 2004/0193250 and 2005/0004651, U.S. Pat. Nos. 6,682,554 and 6,602,285, International Patent Publication No. WO 00/13611, and German Patent Publication No. 19840645, the entireties of which are incorporated herein by reference, disclose endoprosthesis having web elements each formed by a plurality of segments as illustrated in FIG. 2. More particularly, web rings 18 are each formed by a plurality of crown-shaped web elements 20 and are joined one to the other by connectors 22. Each of the crown-shaped web elements 20 is formed by a central member 23a, disposed essentially parallel to the longitudinal axis of the stent in the contracted delivery configuration, and by a first end member 23b and a second end member 23c extending from opposite ends (first end 23d and second end 23e) of the central member 23a at obtuse angles α.
Both of the endoprostheses of FIGS. 1 and 2 include connectors 12 and 22 that are essentially rectilinear in shape. There, those endoprostheses inherently have a limited flexibility and a limited resistance to compressive or torsional forces, for example, to the forces applied to the endoprosthesis during deployment and after implantation. In addition, connectors 12 and 22 offer limited scaffolding to the lumen walls and, if the number of connectors is increased to improve scaffolding (for example, by joining each junction bend in one web ring to a junction bend in a neighboring web ring with a connector), stent flexibility becomes proportionally decreased. Therefore, it would be desirable to provide the endoprosthesis with an elevated degree of scaffolding of the vessel wall while retaining a certain degree of flexibility.